The validity of stability measures: a modeling approach

    Research output: Contribution to JournalArticleAcademicpeer-review

    Abstract

    Measures calculated from unperturbed walking patterns, such as variability measures and maximum Floquet multipliers, are often used to study the stability of walking. However, it is unknown if, and to what extent, these measures correlate to the probability of falling. We studied whether in a simple model of human walking, i.e., a passive dynamic walker, the probability of falling could be predicted from maximum Floquet multipliers, kinematic state variability, and step time variability. We used an extended version of the basic passive dynamic walker with arced feet and a hip spring. The probability of falling was manipulated by varying the foot radius and hip spring stiffness, or varying these factors while co-varying the slope to keep step length constant. The simulation data indicated that Floquet multipliers and kinematic state variability correlated inconsistently with probability of falling. Step time variability correlated well with probability of falling, but a more consistent correlation with the probability of falling was found by calculating the variability of the log transform of the step time. Our findings speak against the use of maximum Floquet multipliers and suggest instead that variability of critical variables may be a good predictor of the probability to fall. © 2011 Elsevier Ltd.
    Original languageEnglish
    Pages (from-to)2401-2408
    JournalJournal of Biomechanics
    Volume44
    Issue number13
    DOIs
    Publication statusPublished - 2011

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    Accidental Falls
    Walking
    Biomechanical Phenomena
    Hip
    Foot
    Kinematics
    Stiffness

    Cite this

    @article{84be2e017e8d46249d1d716b7316e8a0,
    title = "The validity of stability measures: a modeling approach",
    abstract = "Measures calculated from unperturbed walking patterns, such as variability measures and maximum Floquet multipliers, are often used to study the stability of walking. However, it is unknown if, and to what extent, these measures correlate to the probability of falling. We studied whether in a simple model of human walking, i.e., a passive dynamic walker, the probability of falling could be predicted from maximum Floquet multipliers, kinematic state variability, and step time variability. We used an extended version of the basic passive dynamic walker with arced feet and a hip spring. The probability of falling was manipulated by varying the foot radius and hip spring stiffness, or varying these factors while co-varying the slope to keep step length constant. The simulation data indicated that Floquet multipliers and kinematic state variability correlated inconsistently with probability of falling. Step time variability correlated well with probability of falling, but a more consistent correlation with the probability of falling was found by calculating the variability of the log transform of the step time. Our findings speak against the use of maximum Floquet multipliers and suggest instead that variability of critical variables may be a good predictor of the probability to fall. {\circledC} 2011 Elsevier Ltd.",
    author = "S.M. Bruijn and D.J. Bregman and O.G. Meijer and P.J. Beek and {van Dieen}, J.H.",
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    language = "English",
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    journal = "Journal of Biomechanics",
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    The validity of stability measures: a modeling approach. / Bruijn, S.M.; Bregman, D.J.; Meijer, O.G.; Beek, P.J.; van Dieen, J.H.

    In: Journal of Biomechanics, Vol. 44, No. 13, 2011, p. 2401-2408.

    Research output: Contribution to JournalArticleAcademicpeer-review

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    AB - Measures calculated from unperturbed walking patterns, such as variability measures and maximum Floquet multipliers, are often used to study the stability of walking. However, it is unknown if, and to what extent, these measures correlate to the probability of falling. We studied whether in a simple model of human walking, i.e., a passive dynamic walker, the probability of falling could be predicted from maximum Floquet multipliers, kinematic state variability, and step time variability. We used an extended version of the basic passive dynamic walker with arced feet and a hip spring. The probability of falling was manipulated by varying the foot radius and hip spring stiffness, or varying these factors while co-varying the slope to keep step length constant. The simulation data indicated that Floquet multipliers and kinematic state variability correlated inconsistently with probability of falling. Step time variability correlated well with probability of falling, but a more consistent correlation with the probability of falling was found by calculating the variability of the log transform of the step time. Our findings speak against the use of maximum Floquet multipliers and suggest instead that variability of critical variables may be a good predictor of the probability to fall. © 2011 Elsevier Ltd.

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